I think if you couple this with the fact that the restoration hobby is shrinking perceptably, in that there are fewer cars every year to restore (at least the ones we favor), added with the lack of newer inductees to the hobby and the steady loss of the older generations, and the sources begin to dry up. Example - several years back, you could find reproduction AIR tubes for '68 small blocks and/or '68 Z28 applications everywhere. Tried to find those lately ? Made from unobtanium. Need Sealed Power 11:1 forged 327 pistons ? Better hurry. Some things are already pretty scarce.
I believe it's going to be a lot worse than we expect in the short term. Manufacturers are having extreme problems finding and keeping employees, material flow is horrible, low volume production items get cut quickly or obsoleted, maybe never to return. I'm not a pessimistic person, but the alarm bells are going off. If you need it, can aford it, and can find it, better stockpile it.
JMO -
Steve